Cologne leveled her gaze at Mousse and said in Chinese, "For your

inability to win Shampoo as your wife, for your interference in her
marrying Ranma, and for your general lack of respect for not only for
elders but women as well, you are here by banished from the Amazon
tribes."
"An outsider? That means I can become Shampoo's husband by defeating
her." he said as he tried to understand what happened and asked, "Why?"<<

Very well done. You're the first person I've seen who has noticed this. 
Other fic authors have Mousse defeating Shampoo to become her husband, but 
they keep forgetting that that rule applies to outsiders only.